Recently, optical information recording disks are attracting attention as mass capacity information media, although they are not of as large capacity as magnetic tapes. In order for the optical information recording disk to have an increased recording capacity, it often adopts a recording system which records with a constant recording density called a "CLV" (constant linear velocity) system. However, to be applied to information files, that are primarily accessed at random, the disk speed needs to be changed for each access and this results in a slower access time. Because of this, for computer related applications, in which access ability is a crucial performance factor, the "CAV" (constant angular velocity) system is generally adopted. Recently, attempts have been made to achieve both of the virtually constant recording density and fast access by changing the information recording rate while maintaining a constant disk speed. This system is called a "MCAV" (modified constant angular velocity) system. The optical information recording disk and optical information recording disk apparatus based on the above-mentioned conventional MCAV system will be described with reference to the drawings.
FIG. 9 shows the recording surface of the optical information recording disk based on the conventional MCAV system. In the figure, indicated by 66 is an optical guide groove for track 0 sector 0 on the optical information recording disk. Indicated by 67 is an address information recording section in the form of a small pit for track 0 sector 0, in which section are recorded address information including a sector mark, synchronizing VFO signal and track information, and information such as an error check code for the,, address information, all recorded at the time of manufacture of the master disk for the optical information recording disk. Indicated by 68, 69, 70, 71, 72 and 73 are information recording sections for track 0 sector 1, track 0 sector 9, track 1 sector 0, track 1 sector 10, track 2 sector 0, and track 2 sector 6, respectively. Indicated by 74, 75 and 76 are address information sections for track 6 sector 4, track 8 sector 5, and track 9 sector 13. The operation of the optical information recording disk arranged as described above is an follows.
A region extending from an information recording region 66 following the address information recording section 67 for track 0 sector 0 to an information recording region following the address information recording section 73 for track 2 sector 6, and a region extending from an information recording region following the address information recording section 74 for track 8 sector 4 to an information recording region following the address information recording section 76 for track 9 sector 13 have records of different image data of the same number of pixels, and each of these regions occupies 28 sectors. Although these data are recorded dividedly in sectors with a certain information capacity for control or management convenience, they occupy different numbers of tracks due to different numbers of division for compensating the different circumferential lengths at inner and outer portions while maintaining a virtually constant linear density. The worst data transfer rate through recording and reproduction is equivalently 10 sectors per disk revolution, and it is determined by the transfer rate of the innermost track.
Next, the operation of the optical information recording disk apparatus will be described.
FIG. 10 shows a conventional MCAV optical information recording disk apparatus. In the figure, indicated by 38 is a double-sided optical information disk, 39 is an optical head, 41 is a disk spindle motor, 46 is a binary threshold circuit, 48 is an optical head drive control circuit, 50 is an address information detecting circuit, 52 is a PLL circuit, 54 is an error correcting circuit, 56 is a buffer memory circuit, 58 is a laser drive circuit, and 60 is a control microcomputer. The control microcomputer, which implements head tracking on any desired track on the optical information recording disk 38, operates on the optical head drive circuit 48 to have a seek operation for the optical head 39 to the desired target track so that address information read out by the binary threshold circuit 46 and address information detecting circuit 50 matches the desired address. In recording, binary information from the host computer is stored in necessary quantity in a buffer memory 56, and, after being appended with error correcting codes by an error correcting circuit 54, it is written onto the optical information disk 38 by the laser drive circuit 58. In reproduction, a synthesized oscillator in the PLL circuit 52 is set up in advance by the control computer 60 to oscillate the comparing source oscillation frequency corresponding to the target track, and recorded information which was made binary by the binary threshold circuit 46 is read out in response to the reproduction clock produced by the PLL circuit and which frequency is compared with the source oscillation frequency, and, after being rendered error correction by the error correcting circuit 54, it is sent to the buffer memory circuit 56. The data in the buffer memory is then sent to the host computer. The data transfer rate from the host computer at recording or to the host computer at reproduction is in quantity equivalent to 18 sectors per disk revolution at the outermost portion and 10 sectors at the innermost portion. The conventional MCAV optical information recording disk is constant in revolution and, although the concept of "1 track" exists, it has different recording capacities at an inner portion and outer portion, and therefore the number of tracks cannot be correspondent to a certain quantity of information data and, in addition, the maximum information transfer rate is determined by the worst transfer rate of the innermost portion.
However, the foregoing arrangement does not allow the construction of computer systems using the concept of tracks and sectors generally used in digital information recording media, and it requires a correspondence to be made by computation between logical sectors and physical sectors using conversion tables or the like. In general, this computation is intricate and needs accumulation of track numbers with different numbers of sectors starting at the innermost track, and it becomes almost meaningless to record the same track number as a conventional one in the address information on the optical information recording disk.
However, in order to speed up operations such as calculating the number of tracks to be jumped while reading the track address information so as to meet the requirement of faster access on the optical information recording disk, the physical and logical tracks are desirably consistent. Therefore, the conventional arrangement has problems in software overhead to cope with the above matter and increased hardware components for the conversion table. Even though a fast, mass data transfer for digital video data might be accomplished using the outermost portion, the worst transfer rate in the innermost portion negates any improvement over the CAV system. In contrast, the ordinary CLV system successfully overcomes the problem of transfer, however, it necessitates a very high disk revolving speed for recording the innermost portion, creating mechanical problems of vibration and increased access time due to the inertia to follow the disk speed which varies at each access operation.